A Systematic Search for Changing-Look Quasars in SDSS

Abstract

We present a systematic search for changing-look quasars based on repeat photometry from SDSS and Pan-STARRS1, along with repeat spectra from SDSS and SDSS-III BOSS. Objects with large, |Δg|>1 mag photometric variations in their light curves are selected as candidates to look for changes in broad emission line (BEL) features. Out of a sample of 1011 objects that satisfy our selection criteria and have more than one epoch of spectroscopy, we find 10 examples of quasars that have variable and/or "changing-look" BEL features. Four of our objects have emerging BELs; five have disappearing BELs, and one object shows tentative evidence for having both emerging and disappearing BELs. With redshifts in the range 0.20 < z < 0.63, this sample includes the highest-redshift changing-look quasars discovered to date. We highlight the quasar J102152.34+464515.6 at z = 0.204. Here, not only have the Balmer emission lines strongly diminished in prominence, including H$\beta$ all but disappearing, but the blue continuum $f_{\nu }\propto {\nu }^{1/3}$ typical of an AGN is also significantly diminished in the second epoch of spectroscopy. Using our selection criteria, we estimate that >15% of strongly variable luminous quasars display changing-look BEL features on rest-frame timescales of 8 to 10 years. Plausible timescales for variable dust extinction are factors of 2-10 too long to explain the dimming and brightening in these sources, and simple dust reddening models cannot reproduce the BEL changes. On the other hand, an advancement such as disk reprocessing is needed if the observed variations are due to accretion rate changes.

15 pages, 8 Figures, 3 Tables, replaced with version accepted to MNRAS

References in corpus (23)

• The 2.5 m Telescope of the Sloan Digital Sky Survey
• A Catalog of Quasar Properties from SDSS DR7
• The SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Overview and Early Data
• Modeling the Time Variability of SDSS Stripe 82 Quasars as a Damped Random Walk
• AGN Dusty Tori: I. Handling of Clumpy Media
• An ultraviolet-optical flare from the tidal disruption of a helium-rich stellar core
• The Discovery of the First "Changing Look" Quasar: New Insights into the Physics & Phenomenology of AGN
• Space Telescope and Optical Reverberation Mapping Project. II. Swift and HST Reverberation Mapping of the Accretion Disk of NGC 5548
• Testing thermal reprocessing in AGN accretion discs
• Quasar Accretion Disks Are Strongly Inhomogeneous
• The SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Quasar Target Selection
• The Sloan Digital Sky Survey Reverberation Mapping Project: Technical Overview
• AGN Type-casting: Mrk 590 No Longer Fits the Role
• X-Ray and Optical Microlensing in the Lensed Quasar PG 1115+080
• Luminosity Function from dedicated SDSS-III and MMT data of quasars in 0.7<z<4.0 selected with a new approach
• A Consistent Picture Emerges: A Compact X-ray Continuum Emission Region in the Gravitationally Lensed Quasar SDSS J0924+0219
• Measuring Quasar Variability with Pan-STARRS1 and SDSS
• Constraints on the temperature inhomogeneity in quasar accretion discs from the ultraviolet-optical spectral variability
• The X-ray Properties of Active Galactic Nuclei with Double-Peaked Balmer Lines
• An Unobscured type II quasar candidate: SDSS J012032.19-005501.9
• An Improved Photometric Calibration of the Sloan Digital Sky Survey Imaging Data
• The Origin of Wavelength-Dependent Continuum Delays in AGNs - a New Model
• Exploring the Variable Sky with the Sloan Digital Sky Survey

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